Electrical control system



Sept. 27, 1949,- K. E. BARWICK 2,432,892

ELECTRICAL CONTROL SYSTEM Filed oct'. 18, 1946 INVENTOR. //:z'2% Z73417412 Patented Sept. 27, 1949 H ELECTRICAL CONTROLWSXSTEML Keith E.Barwi'ck, Detroit, Michn'assignon: to

Weltronio' Company, Detroit Michi, a corpora? tiomoflMichiganApplication October 18, 194'6,;SerialN'o. 703,982 7 12.ClaimS.. (Cl-315-2168) This invention reiates to electr-ical oontrol systems and isparticularly-"directed toward an. improved and' simplifiedmeans forcontrolling antomatic welding equipment of the-impulse type.

The p i l. objects-of this'inventionareto provide a simplereliable,and-efiicient control of the. aforesaid type; to provide Such a controlwhich, when once energized; willmaintainitself energized until thecompletion of'-'a;i=ull welding cycle irrespective-of the condition ofthe inn ti'ating switchgto providein suoh control a trans- Formerhavinga plurality" of primary windings !arranged inloucking relation;and to generally simplify controls of thetypedescribed.

With the above; aswell-asctlher more detailed objects in' view whichappear from the following description and the appended claims, therei sshown in the-drawings: preferred but illustrative embodiment of theinvention;

In the drawing which is tone-taken as apart of this specificationthere-isillustrated diagram maticaliya controf system embodyingthe-inven tion. r

The control system comprises initiating'net n work 2, .a sequencenetwork I a"- t-i-ming network 6', a firing network 83 and a powernetwork l oso constructed andarranged that the initiatingnet'- work- 2"initiates operation *ofthe sequence network '6 which controls the timingnetwork 5 which in. turn energizes thefiringnetwork 8 for renderingthe'power network 0 conductivei The initiating network 2 comprises apairof discontinuous type 'grid -controlledleading and trailingelectronic valves V'tand V2 and a pair,

- valve SV, the other terminal of rthevalveSV being. connected to theiine' L2. The grid of the valve VI is connected through apa-rallell'yarranged resi-stancejand capacitor to the upperterminal' of" thesecondary windingof the transformer T1 and the "intermediate terminal ofthis winding is connectedto" the cathode of the-valve 'V:l whereby theupper half ;l"1- of thiswinding is operable .to bias'the gridof: thevaiveViwith respect to its'icathode". "I heiower halfof t is samewinding of the transformer .TI'' is :usedias-a primary winding and whitehereinafter -ref erredfto ,asprimary winding l8.

A resistor Rlis connected across the terminals of the primary windinglit has an intermediate tap connection whichisconnected 'hy means ofconductors 2| and 22'- to the line 132 A condenser "Cl is arranged inparaiiel withthelowerportion of the resistor'Rt, and a condenser G2 isconnectedbetween the lower terminator the primary winding 1 8 and thenpper' terminalof the secondary winding t1.

The primary .winding oith transformer T1 has a centertanconhection"dividingit into primarywinding and primarywindi'ng 26; Aconductor '27- having inseries therewith a parallelly arranged resistorR3 and condenser 03- connects the centertan-or'common terminalof thewinding-s 2E and '26 tic-the conductor 22'- connectedto IineLZTheupner'terminal-of thewinding 26 is connected througlrthecontact a ofa time-delay switcl-r TD and throughthe normally open contacts of amanually operated initiating switch SWI to the line Ll while-thedowerterminal of thewinding fl 'i's-directly con-nected by means of conductor28*to-the-l ine ht. The-transformer T2 is arranged to revide-acontrol'loiasrfor the valve V2 and has the upperterminal of itssecondary winding connectedthrough a parallelly arranged resistor andcapacitor tothe' grid thereof and its center tap connection directlyconnected to the cathode thereof; 7 A a'pac-itor C4 is connected betweenthe terminals of lthe secondary winding of thetransformer TZfbrphasecontrol. The up- .per half of the -prirnary' Windingof thetransformer T2 is in zlarailel circuit relation with the valve 'SV,itsnpper'terminalheihgdirectly connected to terminal i6 and-its certtertap being connected through a resistor R54 to theline L2. The lower halfpfthis primary windingis connected between' theiines-Ei and L2- inseries with the resist-MR4.

The sequencenetwork '4 comprises a plurality of discontinuous-typegrid-controlled valves to one tcrm-i'na-lof separatesecondary windingsof a transformer- T3, theprimary winding of wh-i'ch is connected hetweenthe-linesLl and L2.

The-terminals of" the secondary windings of the transformer T3opposite-those connected to the anodesoff -the--va lves V3-'V8 areconnected through impedance networks comprising para-llelly arrangedcapacitorsand resistors to a comcondenser C and variable resistor R5,while the impedance networks associated with the valves V4 and V6 eachcomprise a condenser C6 and a resistor R6 arranged in parallel circuitand having their values so related with respect to each other that eachcondenser C6 is operable to discharge through its resistor R6 in thetime required for the lines LI and L2 to go through two or threecomplete voltage cycles.

The conductivity of each of the valves V4-V8 is controlled by the valvesV3-V| respectively, since the grids of these valves V4 -V8 are eachconnected through resistors to the'terminal of the impedance network ofthe valves V3V'l respectively opposite to that which is connected to thecommon bus 32, so that, for example, if valve V3 is conducting, the gridof valve V4 will be negative with respect to the bus 32. Theconductivity of the valve V3 is controlled by a transformer T4 having asecondary winding, one terminal of which is connected through aparallelly arranged resistor and capacitor to the grid of valve V3 andthe other terminal of which is directly connected to the bus 32. Theprimary winding of the transformer T4 is divided into two parts by anintermediate connection providing primary windings 33 and 34. Thewinding 34 is connected in shunt with the solenoid valve SV by theconductors 35 and 36 connected respectively to the conductors I4 and 21.Conductor 35 is also connected to bus 32 whereby the potential thereofis held at the potential of the terminal l6 of the valve SV. The winding33 is connected between the lines LI and L2 in series with the switchesSW! and TD and a single operation-repeat operation switch SW2. As willbe more fully described hereinafter, the valve V3 is normally maintainedconductive due to the normally de-energized condition of the winding 34and valve SV, but is rendered in a nonconducting or blocked conditionwhen either or both of the windings 33 and 34 are energized.

The timing network 6 comprises a valve V9 controlled by the network 4and a pair of back-toback arranged leading and trailing valves VH1 andVI I. The valve V9 has two controlling grids, either one of which, whenbiased negatively, will prevent the valve from becoming conductive. Thecathode of the valve V9 is maintained at the same potential as the bus32 by a conductor 31' which connects the bus 32 to the cathode of valveV9. One of the controlling grids is connected through a parallellyarranged resistor R1 and capacitor C! to the grid of the valve V4, whileits other grid is connected through a resistance R8 to the grid of thevalve V1 so that valve V9 is operable to conduct only during that timethat both the valves V4 and V1 are conductive. The anode potential forthe valve V9 is supplied by a transformer T5, the primary winding ofwhich is connected in parallel with the solenoid valve SV by means of aconductor 38, having a manually operated weld-no weld switch SW3 and apressure-actuated switch SW4, connected from one terminal of the primarywinding to the line L2 and by a conductor 40 which connects the otherterminal of the primary winding to the bus 32. It will be noted that thebus 32 is connected by conductor 35 to the conductor 14 which is in turnconnected to the terminal I6 of the actuating coil of the solenoid valveSV. 4

One terminal of the secondary winding of the transformer T5 is directlyconnected to the anode of the valve V9, while the other terminal isconnected by conductor 42 to the cathode of the valve VII). The grid ofthis valve is connected by a conductor 44, having in series therewith aparallelly connected resistor RH] and capacitor Clo, to the cathode ofthe valve V9. A capacitor CM is connected between the cathode of valveV3 and conductor 42. One terminal of the secondary winding of atransformer T6 is connected to conductor 42 and the other terminal ofthis secondary winding is connected through a parallelly arrangedresistor R9 and capacitor C9 to the grid of the leading valve Vlll. Aresistor Rl2 is connected between the grid and cathode of valve V15 toinsure that the valve Vlfl conducts immediately after the valve V8conducts and the anode of valve Vlil is positive. The primary winding ofthe transformer T6 is connected between the lines LI and L2 byconductors 45 and 48 so that it is continually energized as long as theline switches LS! and LS2 are closed and is polarized so that its outputvoltage will be effective to render the grid of the valve V10 negativewhenever the potential of the anode of the valve VI 5 is positive withrespect to its cathode. However, when the valve V9 is conducting, thepotential of transformer T5 opposes that of the transformer T6 so thatthe grid of the valve Vil'l'will be properly biased to permit the valveVlll to conduct.

The anode of the valve Vifi and the cathode of the valve Vll areconnected together and to the line L3 by a conductor 58, while thecathode of the valve VH) and anode of the valve Vii are connectedtogether and to line L4 by a conductor 52 having in series therewith theprimary winding of a kick transformer Tl. The primary winding of atransformer T8 is continually connected between the lines L3 and L4, oneterminal being connected to the conductor 55 by a conductor 54 and theother terminal being connected to the portion of the conductor 52between the transformer T1 and line L4. One terminal of each of thesecondary windings of the transformers T1 and T8 are connected togetherby a conductor 55. The other terminal of the secondary winding oftransformer Tl is connected through a parallelly arranged resistor andcapacitor to the grid of valve VI I, while the other terminal of thesecondary winding of the transformer T8 is connected through theconductor 54 to the cathode of valve VI I. The voltage of thetransformer T8 is such that it is efiective, when acting alone, torender the grid of the valve Vll negative with respect to its cathodewhenever the anode of valve VH is positive with respect to its cathode.The kick transformer T7 is arranged so'that Whenever the valve Vlfl isconductive during a half cycle of current, the collapse of flux thereinholds the grid of the valve VII in condition to permit the valve Vii toconduct during the subsequent half cycle. The valve VII therefore willnot conduct unless the valve Vlll has conducted during the precedinghalf cycle and will always conduct during a subsequent half cycle to ahalf cycle that valve VII] conducts.

The firing network 8 comprises a transformer T9, a saturable reactor 56,and a current-limiting reactor 58. One terminal of the primary windingof the transformer T9 is connected by a conductor to the conductor 42,while the other terminal is connected through the saturable reactor 56and current-limiting reactor 58 to one terminal 62 of a weldingtransformer WT having its other terminal directl connected to the lineL4. A switch SW4 is arranged to shunt out the reactor 58 when lines L3;and L4 are supplied reassess with" 220=volt. power" and to opened" when7 {Mill-volt" power is being supplied? When" the valves V I andLV'll areconducting current will flow between the lines"L3;"and?I-i4' through"the conductor 58, valvev'lflor"V1'l,i,conductors 52 and" 6t, reactors56fand -58, and the Welding transformer WT"to' energize the transformerT9? Apair ofsecondary-'wirrdings'oftransformer T9 are-connectedrespectlvelrthrouglr rectifiti's Ell-"and 86470 the ignitersand"cathodesofmer cury pool-type"-power=controlling *valves-v l'z andV'l3" respectively: It* wil l be" noted" that when the valves-V lli'and"Vl"l"cond1ict, the transformer T9 and reactors (hand 58 "are in"p'arallel circuit with thewalves V|2and'- V P3? and the" potentialthereacross is the potential betweenthe-cathodes and anodes of thepoweFcontrolli-ng' valves: Therefore;when thewalves Vl or Vl3 fire; theigniters are" practicallyde=energizedy and no deteriorating voltagei'smaintained onthe igniter of the valves 'Vl '2"an'd V t3? Reactor5'8is adj ustable in its timerofsaturationt'oprovide forfir ing' the valvesV I 2" and V Hi adjustable points alongthevoltage wave-between"the-lines I23" and L4--to-provide for controlling the welding heat as ismore-fully--described=' and-claimed-in the co-= pending application-0Pletus-=J i oilorn,-' Serial No. 681,758; filed='July- 65 19465 andassigned to the'same a'ssignee as i's-the-present invention;

' It is thoughtthatthe-remaining detailsyof'the system may best beunderstood with reference to a description of the operation thereof.Assuming; that it is "desiredto condition theisystemforrepeat-operati'on; the switch- SW2 is opencircuitedan'd- 'the usual-disconnect line switches LSP and-'LS2' are'-'closed-, therebyconnectingthe lineconduct'orslll and L'Ftothesourceof supply which maybe aconventional GO cycle alternating current 1l0'-volt* system: Thedisconnect line. switches LS3 -and-"L'Sfl; which may bemechanicallyconnected to the switches" LSI and LS2; are also closed; therebyconnectingthe line conductors E3 and BF to-a suitable source of supplywhich ma be -a-- conventional (Sir-cycle alternating current 220 on440=volt system,

switch SW i beingset accordingly-as hereinbefore described.-Erlergization 0f the lines Iil and L2 energizes primar winding- 24of-the'transfonner T! I and the lower h-al-f=- of fthe primarywindin'gof thetransformer-{I 2 whereby-a--biasingvoltage is applied between' thegrid andcathode' of the valves V1 and V2 respectively- 'to-maintain thevalvesin a bloeked condltionr Closure of' the line switches-LS1 and--ESZalso energizes the transformer T3 having a secondary winding; theterminals of which; 'as--ii'1dicated Icy-the letters ma: appearing-"0nthe-winding and on the cathode heaters, are connected to energize thecathode heaters' of the valves- -Vl vl l inclusive; The transformers Tfiand Tlhwere alsoenergized upon closure of the line:switchesBSI a-ndESEtQ pro vide respectively: a blockingbias voltage between the-grid andcathoderofifthe-valVes:-V le and V i 1i Glosure; of? the; line"switche'sazllsiit'. and: Lslltzpree pared the:- firingmetwork: &andsthe' power net.-' work: ilixfor: operations-by theenetwork; 4-Enemgization-of- -the-.-transformem'Il3-saiso energized the time-delay?means TD- whichsispoperable after a predetermined. timewdelay tocloseits contacts 11, whereby -v theinitiating,i network limay beoperated the. closure of'.the .switch' 'SWI. As soon as the valves V3--V8 inclusiveare allfrendered in an operative condition due toheating"ofth'eir cathodes by their" respective cathode heaters," the valves V3,V5? andV'Fwi'll becomeconductive placed across the primary windings33"'and' 34;

and therefore the grid of the valve" V3" will be at the same potentialas the cathode thereof due to its-int'erconnectionthrough the secondarywinding of thetransformer T4 which is connectedbetweemthe-grid andcommon" cathode bus 32}; Conduction" of the valve vscauses' apotentiatdrop to appear across the time-delay means T133whichma-intainsth'egri'd of the valve V l negative with-"respect to the bus 3-2"a-ndthe va1ve-V4 blockedr Since nocurrent is flowing in the anode' circuitofthe valve V4; there will be no drop across the impedance networkthereof comprising the" resistor R6 and capacitoncfi so that whe -gridof the -valve=V5=will-=beat the same potential as the cathode thereof"and this valve wil l-be= conductivea Conduction of the valve V5 causes apotentialdroptoappearacross the time del'ay network TD5 which -willmaintain the grid of "the-valve V5 hegativewith respect to thecathodethereof, and-the--valv -V6 will therefore be in a blockedcondition; Sinceno current is flowing through: the impedanc'e network ofthe valvevtg: the grid of thevalve V-F'Will be maintainedat the samepotential as the cathode thereof," andthe valve VT will 'hein aconducting condition, causing current to flow through its time-delay"networ-k TDT, thereby maintaining the grid ofthe valve V8negative'--with respect to the cathode thereof; and- 'th'e valve V8 willbe heldiblocked; The" rig-ht-h-and grid of the valve V9. which.isconnected to-thegrid'--of thevalve Vk will beirnaintained atthesameipotential with respect; touits cathode as the grid of the valveV'lfwithz respect to its-cathode: I

Since the valve VE:.:is: not: conducting, V the conductor 96: which? is;electrica'll y'- connected to the terminal of the impedance-network: ohthe valve VltoDDosite to' th'at connected to thebus -32:and' to thegrid0f31 the valve VI: is conducting-current from: the upper terminal-Qof. the w-inding 17 through the impedance net-work TD8,- the common".busi32r: and conductor 35 backi to the lowerttermina'lxofCthe'windingHi? This conduc tion: is without anyoperational effect uponthe system;since the: potential 'suppli'edbythe wind ing it? is quite sufiicient tomaintain the grid in a condition to -block-the valve VI inspite of theadded potential drop =through the resistor in the grid circuit ofithevalve VI:

Before a: stabilized condition of: the valves V-3-V8 isv reached;certain: of these valves may fire out oia' orders because- Ofithe factthat they have notas yet had the proper biases placed betweentheir:grids andcathodesi Such operation is-withoutjeffect; however, due"to the; open condition: ot the: switch SW4- which is. controlled bytheoutlet fluid pressure: of the solenoidrvalve SV; The: switch SW4 isclosed. only when: the valve SV is inopen positi'on :and-iadpredetermined fliiid pressure is :being- =supplied 'to hold the: weld=ingelectrodes E against the work W: The solenoid valve SV has not: asyet been energizedcbecause. of the biasb'eing continually placed.between the gridand cathode 'of the valves V I and VZx-by thetransformers-Tl and -TZJ The valvesmvlflif and V13-- can= onlyfires-ub'sequent to :thefiringmf'zthe valves V10 and Vl l; and thesezvalves:areilikewis'e continually maintained in a blohedi condition After apredeterminedf ti-iner delay;- whiohui's sufiiciently ample to permitall of the valves V3-V8 to come to their stabilized condition, thenetworks 2, 4, 6, 8, and ID are ready for operation. Before a weldingcycle can be initiated, the switch SW3 must first be closed. The switchSWI is then closed, energizing the primary winding 26 of the transformerTI, which energization acts to buck the flux in the core thereof due tothe primary winding 24. This removes the blocking bias between the gridand cathode of the valve VI and the valve VI conducts. Conduction of thevalve VI causes current to flow from the line LI through the conductorI2, the valve VI, conductor I4, and the energizing coil of the solenoidvalve SV to the line L2. At the same time, current also flows from theline LI through the upper half of the primary winding of the transformerT2 and the resistor R4 to the line L2, through the winding I8 oftransformer TI, the lower portion of the resistor RI and capacitor CI,and through the primary winding 34 of transformer T4, which circuits arein shunt relation to the valve SV.

Current through the winding I8 aids the current flow through the winding26 in its bucking effect of the flux produced in the core of thetransformer TI by the current flow through the winding 24. If the switchSWI at this time is still in closed position, this is withoutsubstantive effect on the operation of the network 2 other than to placeon valve VI a bias somewhat more favorable to its already conductivecondition. Current flow through the winding 34 of transformer T4 placesa blocking potential between the grid and cathode of the valve V3 andrenders the same nonconductive at the end of its conducting half cycle.Current flow through this upper half of the primary winding oftransformer T2 tends to buck the fi-ux due to current flow through thelower half of this primary winding so that, at the next half cycle ofthe voltage wave between the lines LI and L2 when the anode of the valveV2 becomes positive with respect to the cathode thereof, the grid of thevalve V2 will not be immediately rendered negative with respect to thecathode thereof due to the phasing effect of the capacitor C4 and theimpedance of the primary winding of the transformer T2 so that the valveV2 will become conductive. Conduction of the valve V2 again establishesthe circuit through the energizing winding of the solenoid valve SV andthe windings I8 and 34 and upper half of the primary winding oftransformer T2 as above identified, except that it flows in the oppositedirection and through valve V2 instead of through valve VI. As the fluxcollapses in the core of the transformer TI at the end of the half cyclein which the line L2 is positive with respect to the line LI, thecondenser C2, which was charged during this time, discharges through thewindings I I and I8 arranged in series connection which opposes thebuild up in flux in the core of the transformer TI due to energizationof the primary winding 24, so that the grid of the valve VI is notrendered negative with respect to the cathode thereof and the valve VIis rendered conductive. This subsequent conduction of the valve VI afterinitial conduction due to closure of the switch SW I will continue inthe above-identified manner irrespective of the open or closed circuitcondition of the switch SWI and will be terminated only upon completionof the full cycle of operation of the sequence network 4 in a manner tobe hereinafter described.

After the circuit through the energizing coil of the solenoid valve sVwas energized, the primary winding 34 of the transformer T4 was alsoenergized as hereinbefore described. This caused a voltage to be inducedin its secondary winding which biases the grid of the valve V3 negativewith respect to its cathode to render the valve V3 nonconductive. Thisrendering of the valve V3 nonconductive is without immediate effect dueto the potential maintaining feature of the time-delay means TD3.Subsequent to. a predetermined time interval after blocking of the valveV3, the capacitor C5 of the time-delay means TD3 will have dischargedthrough its associated resistor R5 to render the grid of the valve V4 atthe same potential as the bus 32. This time interval between the timethat the solenoid valve SV was energized and the time that thetime-delay means TD3 is timed out so that the grid of the valve V4 isrendered at the same potential as the bus 32 is the clamping or squeezetime of the welding apparatus-and represents the time interval betweenthe time that the welding electrodes E1 were brought against the work Wand the time that the valve V 9 is rendered conductive to initiate flowof welding through the welding transformer WT. As the time-delay meansTD3 times out, the left-hand grid of the valve V9 will no longer bemaintained negative with respect to the cathode thereof, and since theright-hand grid of the valve vs at this time is at cathode potential,the valve V9 will conduct and oppose the potential of the transformer T6to render the valve Vi a conductive. As the valve VII) becomesconductive, current will flow from the line L3 through the conductor 50through the valve VII) and conductors 32 and 6!! to the primary windingof the transformer T9. From the primary winding of the transformer T9,the current flows through the saturable reactor 56, the current limitingreactor '58, and the primary winding of the welding transformer to theline L4. At a predetermined time interv-al, which is always a fractionof a half cycle of the voltage wave between the lines L3 and L4, thesaturable reactor 56 will saturate, permitting the critical voltage tobe supplied by the left-hand secondary coil of the transformer T9between the igniter and cathode of the valve VI2 to render the valve VI2conductive. Conduction of the valve VI2 causes current to flow from theline L3 through the valve VI2 and the welding transformer WT to the lineL4. Conduction of the valve VII'I also causes current to flow throughthe primary winding of the transformer T1 to the line L2, so that at theend of this half cycle during which the line Ll was positive withrespect to the line L2, the collapse of flux in the kick transformer T!will induce a potential in the secondary winding thereof which overcomesthe potential induced in the secondary winding of the transformer T8 sothat the grid of the valve VII is not rendered negative with respect toits cathode before the valve VII conducts. Once conducting, the valveVII will permit current to flow from the line L4 through the primarywinding of the welding transformer WT, the reactors 56 and 58, thetransformer T9, the conductor 60, the valve VII and conductor 50 to theline L3. The flow of current through this just-mentioned circuit,depending upon the time taken to saturate the saturable reactor 56, willcause the critical potential to be applied between the igniter andcathode of the valve VI3 for rendering it conductive to permit currentflow from the line L4 through the welding transformer WT, the valve VI3back to the line L3.

ewa e .At the time the time-delay means 'ID3 timed out the valve V4 wasalso renderedoonductive, causing a potential 'tob'e established acrossits anode impedance .eircu'it, "thereby reifdering'the grid of the valveV negative with res ectto its cathode to block the v'alveV5. "Therendering of valve V55 nonconductive is 'w'ithout immediate effect due .tothe"time-delay network -TD5 which maintains "the grid of the valve VBnegativeand consequently the valve voblocked 'for..a .prede terminedtime intervalsubsequent to blockingof the valve V5. This time intervalisthewelding time, since at the expiration of this time interval the :gridof the valve V 6 "w'illbe rendered at cathode potential and valve V6will become conductive. Upon conduction of valve V6 a .potential will beestablished across v-the impedance .network of its anode. circuit,rendering the grids" of the valves V and V9 negative with-respect totheir cathodes andconseguently the valves nonconductive. The meansTD5-therefore controls the welding time or vinterval whenvalve V9 isconductive.

Rendering of-the valve Vl' blocked without immediate -efi'ect,'=but--assoon as the-' time-delay means TD! times -out,'-thevalve V8 will berendered 'conductivewbec'ause' its grid will then be' at cathodepotential. The time interval represented by the time of themeans TDl isthe hold'time or time that thecelectro'des Ear e held against the work-W during cooling'of the weld. i Conduction of the valveVBestablishesap'otential 'acrossits time-delay means 'TDfi whic'h rendersthe potential of the conductor" 66: negative with respect to the bus 32and 'withre'sp'ect to' the cathode of valve Vi Whichis connected theretobythe conductors ill and ..:35."'The negative potential of the conductor66 is ofsuilicient magnitude to hold the grid of 'thevalve VI negativewith respect to its associatedcathode andfhold the valve Vl againstsubsequent fir ing, thereby de-energizing the solenoid valve ='SV-andpernii-ttingthveleotrodes E to'be released from the work W. The valve'VZwill not aga'in berendered conductive, since theupper half'ofthe-primarywinding'o'f transformer T2 was 5 likewise "de-energized, permitting thelower half-ofthis winding to bias the valve V2 nonconductive. I

Winding "34 which is also in parallel circuit with the valve 'SV is alsod'eeenergizedi to initiate the resetting cycle of operation "of thesequence networkd by removing theblocking'b'ias onvalve' V3 so that itis rendered conductive. Conductionof valve V3 ire-establishes thepotential drop across its anode impedance network rendering the-valveVii blocked which rem o'ves the bloekin'g biason the grid of valve V5.Valve V5 then becomes conductive, 'establishing,'du'e to "thepotentialdrop across itstime-delay means T135, ablocking bias on thegrid of valve'Vt, rendering this valve nonconductive. With valve V6n'onconductive, the grid of valve Vl goes-'to oathodepotential, andvalve 'V'l becomes conductive, ire-establishing a potential drop acrossits "time-delay means'T-Dl, rendering the grid of valve V8 negative withrespect to its cathoda and valve V8no'nconductive. Rendering of valveV'8 blocked iswithout immediate e'fiect, duetogthe action -01:'the'ti'm'e-delay means TDB which will maintain a potential thereacrossfor a predetermined timeinterval subsequent to the blocking iofthevalveThis'interval is the ofinme peneaof'the welding-machine or time when ithe electrodes E are maintained parted.

As the time-delay times out, the

iv dfsaid first controlling "iiieans "ior 'rendering negativewpotential.impressed thereby. on the grid of'the valve 'vl disappears, and,assuming the switch SWI to.be closed indicating-that'the'desired.welding has 'nb'tlbeen cemented, the valve Vi williagain 'be renderedconductivein the same mariner .as is described herei'nb'fore, and theweldingicycle will "be repeated. If, however, the sw-itc'h SW1 has been.opened, the networks will remain in'this stable. condition until "theswitch SW1 is again closed, because theonlylprimary or input winding of"the transformer'T'l which is energized is windingid, .and the eifect ofthis winding is I to maintain v'a'lve 1V1 iblocked.

-Ii now the sw'itchS'Wlhad been in closed -circuitorsingle-weldposition-the cycle ofoperation just {described in..connection with the repeat w'eld or open-circuit condition of switchSW2 would'bel'iriterrupted'at thel time valve V8 was rendered conductiveand betore theresetting-cycle of network 4-was initiated. interruptionis due toftheenergization ofthe windingteof transforme'r'T4, whichis.p'oflarfizedso that curreritflow therethrough .aids the'current flowthrough the winding 34 in p'laei'nga blockinglbiaspotential on thegrido'fthe valve' V3. 'The vallvelfi, therefore, will remain in ablocked orlnonconductive condition, even thoughlthe w1n&in 4:d-e-energ'ized dueto the nonconductive conditionof the valves V l. and"V2. 'Sincethe valve Vl'iis maintained blocked, the ntworlail can-notgothrough its resetting cycle of operation andwill-remain in thatcondition "as longas thesw itch swl remains closed. OpeningOfthQ-SVitChjS'Wl de-energizes thew'in'ding 33, permitting valve V3:tobecome conductive and the resetting cycle of network l tooccur: inthemanner h described in connection with the repeat operation. 115,however, the switch SWI is openedprior-tothecompletion of theinitiaLportionof the"operation of "the sequence networ kdthe-weldingcycle will continue through. its. resetting cycle .-just-asthe switch SW; rwerein repeat or open-zpos-ition, but, as set forth withrespect to the repeat operation, another welding cycle-will not:beinitiated, because atthis time only thew-hiding?! o'fltransformer Tl. is?energized,'fland"this winding acts to hold the valveiv'l blocked.

Ihe 's'witch SW3 is normally maintained in closed circuit positionbutmay be'opened 'in the 4 event it is 'desiredto "go throughall ofzthewelding steps without-welding current -actually flowing. Switch SW4prevents welding cur-rent from flowin'g'in'the event the'iiuidpressureto the electrodes failsffor any reason.

.Althoughonly ae-sing-le specific embodiment of the invention has-been:disclosedtin-detail, itw-ill be -appreciated -that various modificationsin the form,- number, and: arrangementt'ofqaarts may be made withoutdeparting from the spirit and scope 0f the invention.

What is claimedandis'desired to 'be'secured by TinitedStates'LettersTatent is as'fo'llows:

1. in an electrical controlling network, electronic valvemeans having acathode and a controlling gridypotentialsupplying means electric'a'lly'connectedbetwe'en';said"cathode and said grid 'for applyingabi'aspotential to eontro1 the conduction of saidvalve means, means forcontrolling the magnitude fol? said, potential applied hetwe'en' said-cathode and'said grid and operable uponenerg'ization' to'rendersaldsupplying means ineffective to 'supplys'a'i'd bias'potential, and asecond controlling means"energizediindependent- 11 said supplying meansinefiective to supply said potential.

2. In an electrical controlling network, a pair of electronic valvesconnected back to back, one ofsaid valves having a cathode and acontrolling grid, potential supplying means electrically connectedbetween said grid and said cathode for biasing said grid with respect tosaid cathode for maintaining said one valve nonconductive, meansrendering said biasing means ineffective to supply said potential, andmeans energizable as a consequence of an operating condition of theother of said valves for rendering said biasing means ineffective tosupply said potential.

3. In an electrical controlling network, a transformer having a singlecore and a plurality of windings, each said winding having a pair ofterminals, an electronic valve having a cathode and, a controlling grid,circuit means connecting the terminals of one of said windings betweensaid grid and said cathode, circuit means connecting the terminals ofanother of said windings across a source of electrical supply potential,and means electrically connecting the terminals of a third of saidwindings to said supply potential in opposite polarity relative to theconnection of said other winding whereby current flow through said thirdwinding opposes the build up of flux in said core due to flow of currentthrough said second winding thereby to vary the voltage output of saidfirst winding.

4. In an electrical controlling network, a pair of terminals adapted tobe connected to a source of alternating current supply, a pair ofelectronic valves, each of said valves having a cathode and an anode anda controlling grid, circuit means connecting one of said terminals tothe anode of one of said valves and to the cathode of the other of saidvalves, circuit means connecting the other of said terminals to thecathode of said one valve and to the anode or said other valve,translating means in series circuit with one of said circuit means,transformer means having a first winding connected between saidterminals and a second winding connected between the cathode and grid ofsaid one valve, a third and a fourth winding for said transformer means,a controlling switch, a circuit connecting said third winding to saidterminals through said switch, and a circuit connecting said otherterminal through said fourth winding and one of said valves to said oneterminal.

5. In an electrical controllingnetwork, a pair of terminals adapted tobe connected to a source of alternating current supply, a pair ofelectronic valves, each of said valves having a cathode and an anode anda controlling grid, circuit means connecting one of said terminals tothe anode of one of the valves and to the cathode of the other of saidvalves, circuit means connecting the other of said terminals to thecathode of said one valve and to the anode of said other valve,translating means in series circuit with one of said circuit means,transformer means having a single core, a first transformer windingconnected between said terminals and a second transformer windingconnected between the cathode and grid of said one valve, a third and afourth transformer winding for said transformer means, a controllingswitch, a circuit connecting said third winding to said terminalsthrough said switch, and a circuit connectingsaid other terminal throughsaid fourth winding and one of said valves to said one terminal, saidfirst winding being operable to induce a flux in said core in onedirection whereby a bias voltage of one por 12 larity is applied by saidsecond winding to said one valve, said third and fourth windings beingso polarized relative to said first winding that current flow througheither thereof will oppose the flux in said core due to current flowthrough said first winding.

6. In an electrical controlling network, a pair of terminals adapted tobe supplied with alternating current energy, a working circuit betweensaid terminals including a pair of back-to-back arranged Valve means,whereby alternating current fiow therethrough may be controlled, each ofsaid valve means having an anode, and a controlling grid and a cathode,a transformer having a single core and a plurality of windings aboutsaid core, one of said windings being connected between the grid andcathode of one of said valves, a second of said windings being connectedbetween said terminals and arranged'to render the potential of the gridof said one valve negative when the potential of its respective cathodeis negative with respect to its anode, a switch, a third of saidwindings being connected through said switch to said terminals andarranged to buck the flux in said core due to said second winding, and afourth of said windings connected to said terminals through the other ofsaid valves.

7. In an electrical controlling network, a pair of terminals adapted tobe supplied with alternating current energy, a working circuit betweensaid terminals including a pair of back-to-back arranged valve meanswhereby alternating current flow therethrough may be controlled, each ofsaid valve means having an anode and a controlling grid and a cathode, atransformer having a single core and a plurality of windings about saidcore, one of said windings being connected between the grid and cathodeof one of said valves, a second of said windings being connected betweensaid terminals and arranged to render the potential of the grid of saidone valve negative when the potential of its respective cathode isnegative with respect to its anode, a switch, a third of said windingsbeing connected through said switch to said terminals and arranged tobuck the flux in said core due to said second winding, a fourth of saidwindings connected to said terminals through the other of said valves,and capacitor means connected to said first winding whereby it isoperable to discharge therethrough to provide a lagging output Voltagefor said second winding relative to that between the anode and cathodeof said first valve means.

8. In an electrical controlling network, a pair of terminals adapted tobe supplied with alternating current energy, a Working circuit betweensaid terminals including a pair of back-to-back arranged valve meanswhereby alternating current flow therethrough may be controlled, each ofsaid valve means having an anode and a controlling grid and a cathode, atransformer having a single core and a plurality of windings about saidcore, one of said windings being connected between the grid and cathodeof one of said valves, a second ofsaid windings being connected betweensaid terminals and arranged to render the potential of the grid of saidone valve negative when the potential of its respective cathode isnegative with respect to its anode, a switch, a third of said windingsbeing connected through said switch to said terminals and arranged tobuck the flux in said core due to said second winding, a fourth of saidwindings connected to said terminals through the other of said valves,ca-

pacitor means connected to said first windin whereby it is operable todischarge therethrough to provide a lagging output voltage for saidsecond winding relative to that between the anode and cathode of saidfirst valve means, and means for limiting the magnitude of current flowthrough said second and third windings.

9. In an electrical controlling network, a pair of terminals adapted tobe supplied with alternating current energy, an inductive workingcircuit between said terminals including a pair of backto-back arrangedvalve means whereby alternating current flow therethrough may becontrolled, each of said valve means having an anode and a controllinggrid and a cathode, a transformer having a single core and a pluralityof windings about said core, one of said windings being connectedbetween the grid and cathode of one of said valves, a second of saidwindings being connected between said terminals and arranged to renderthe potential of the grid of said one valve negative when the potentialof its respective cathode is negative with respect to its anode, aswitch, a third of said windings being connected through said switch tosaid terminals and arranged to buck the flux in said core due to saidsecond winding, a fourth of said windings, capacitor means connected tosaid first winding whereby it is operable to discharge therethrough toprovide a lagging output voltage for said second winding relative tothat between the anode and cathode of said first valve means, resistancemeans connected across the ends of said fourth winding and having a tapintermediate its ends, circuit means connecting said tap to one of saidterminals and one of said fourth winding to the other of said terminals,and capacitor means connected between said tap and the other end of saidfourth winding.

10. In an electrical controlling network, a pair of terminals adapted tobe supplied with alternating current ener y, a working circuit betweensaid terminals including a pair of back-to-back arranged valve meanswhereby alternating current flow therethrough may be controlled, each ofsaid valve means having an anode and a controlling grid and a cathode, atransformer having a single core and a plurality of windings about saidcore, one of said windings being connected between the grid and cathodeof one of said valves, a second of said windings being connected betweensaid terminals and arranged to render the potential of the grid of saidone valve negative when the potential of its respective cathode isnegative with respect to its anode, a switch, a third of said windingsbeing connected through said switch to said terminals and arranged tobuck the flux in said core due to said second winding, a fourth of saidwindings connected to said terminals through the other of said valves,capacitor means connected to said first winding whereby it is operableto discharge therethrough to provide a lagging output voltage for saidsecond winding relative to that between the anode and cathode of saidfirst valve means, and capacitor means in series circuit with saidsecond and third windings.

between the grid and cathode of One of said valves, a second of saidwindings being connected between said terminals and arranged to renderthe potential of the grid of said one valve negative when the potentialof its respective cathode is negative with respect to its anode, aswitch, a third of said windings being connected through said switch tosaid terminals and arranged to buck the flux in said core due to saidsecond winding, a fourth of said windings connected to said terminalsthrough the other of said valves, capacitor means connected to saidfirst windin whereby it is operable to discharge therethrough to providea lagging output voltage for said second winding relative to thatbetween the anode and cathode of said first Valve means, and a secondmeans for biasing the grid of said one valve independently of said firstWinding.

12. In an electrical controlling system, a sequence controlling network,an initiating network for initiating the operation of said sequencenetwork including a pair of back-to-back arranged electronic valves eachhaving a controlling grid and a main electrode, transformer means havinga secondary winding and a plurality of primary windings, each saidwinding having a pair of terminals, means connecting said terminals ofsaid secondary winding between said grid and main electrode of one ofsaid valves, to control the conduction of said one valve, means adaptedto connect a source of potential to said terminals of one of saidprimary windings operable to normally maintain said. one primary windingenergized whereby said secondary winding is operable to supply apotential to bias the grid of said one valve into a blocked condition,means for selectively connecting the terminals of a second of saidprimary windings to a source of potential in a direction to oppose theenergization of said transformer means by said first primary winding,potential supplying means including the other of said valves connectedto the terminals of a third of said primary windings for energizing saidthird primary winding, in a direction to oppose the energization of saidtransformer means by said first primary winding, and potential supplyingmeans connected between said grid and said main electrode of said onevalve and controlled by said sequence network for biasing said grid andsaid cathode of said one valve with respect to each other.

KEITH E. BARWICK.

No references cited.

